The resolution of a display, the main output unit in a computer system, is becoming higher year by year, thereby allowing an image to be displayed in greater detail. This is because the performance of a graphics accelerator that is installed in the computer system and the performance of the display is improved.
On the other hand, the size of the display screen of a display apparatus for displaying images cannot unlimitedly be increased because of physical limitations of the display apparatus itself. A flat panel display included in a notebook computer, for example, cannot be much larger than the main unit of the computer because of its notebook shape and therefore the size of its display screen is limited as a necessity. Also a display, especially a CRT display, in a desktop computer, cannot be made unlimitedly larger in terms of its footprint and weight because the display apparatus is placed on a desk.
Conventionally, therefore, dots, which are minimum display units, are made smaller to achieve higher resolution for a display screen of limited size.
While the amount of information displayed on the display screen can be increased by reducing a dot size to provide a higher resolution, the size of an image and character is also reduced by the reduced dot size, thereby degrading the visibility of the content of the display.
A unit for zooming in on a portion of a display screen is provided in most of today's computer systems in order to improve visibility of the display content to visually impaired users. This unit can be used to improve visibility of an image and character the size of which is, as mentioned above, reduced by increased resolution.
Windows 98 and Windows NT, which are operating systems from Microsoft Inc., include a tool called “magnifier” as standard. This tool opens a special window used for displaying an enlarged image, and enlarges and displays a portion in the vicinity of the mouse cursor or key cursor in this special window in real time.
FIG. 1 shows a conventional display image zoomed in by the magnifier on a display screen. In FIG. 1, an area labeled with 401 is the area where an image zoomed in by the magnifier is displayed.
A notebook personal computer from IBM contains, in addition to the above-mentioned tool supported by the OS, its own tool for enlarging an image in a rectangular area in the vicinity of the mouse cursor.
FIG. 2 shows a conventional display image zoomed in by this magnification tool on a display screen. In FIG. 2, an area labeled with 501 is the area where an image zoomed in by the magnifier tool is displayed.
Problems to be Solved by the Invention
Conventionally, when a higher resolution is provided by reducing dot size, the size of an image and a character is also reduced with the reduced dot size, thus degrading the visibility of the content of the display, as described earlier. To solve the problem, a unit for zooming in on a portion of a display screen, which is conventionally provided in a computer system, may be used. However, such a technology cannot provide an environment having adequately high visibility to the user.
That is, such types of technology zoom in only on a predetermined area on a display screen. Therefore when a large window or area in which an enlarged image is displayed is provided on the screen, the other areas on the screen are hidden by the window or area to degrade the visibility of the display.
Furthermore, because all of these technologies use software to zoom the image, significant CPU overhead is introduced, thus limiting the size of the area that can be zoomed, and reducing the display speed when a large area is zoomed in.
It is an object of the present invention to allow for switching between a normal display and a zoom display by a simple operation, thereby providing both of a large amount of information achieved by high resolution and high visibility of the display.
It is another object of the present invention to zoom in on a display screen by using hardware unit without placing stress on a user.